In an internal combustion engine where action by the intake valves is used to throttle the engine as opposed to action by a throttle valve, a new strategy for controlling nitrous oxide (NOx) emissions is required. In an engine throttled by a throttle valve, a vacuum condition is established in the intake manifold at low operating speeds due to the pressure drop across the throttle valve while the engine continues to draw from the intake manifold. This pressure drop across the throttle valve may be used to draw recirculated exhaust gases back through the intake manifold and into the engine for recombustion. By contrast, in an engine where the throttling function is performed by the intake valves, there is an insignificant pressure drop between the exhaust and intake manifolds which necessitates a relatively large flow area therebetween in order to recirculate sufficient exhaust gases to the intake and ultimately reduce NOx emissions.